There are many problems to be overcome in the metalizing of materials. Some of the conventional methods for metalizing include electrolytic, sputtering and autocatalytic processes. Such conventional methods may result in uneven coating, clumping and flaking of the metal deposited on the material. Autocatalytic baths often have “dead zones” within the bath solution, where no metal application occurs.
In the field of medicine, the aerospace industry, and for other industrial applications, it is desirable to provide a process for deposition of metals onto a material that results in an even application of metal onto the material. Without stringent control of the thickness of a metallic coating, large quantities of metal may be wasted by applying an excessively thick layer, or the effectiveness of a metal layer may be reduced if an area of thin application results. With such problems as these, it is difficult to achieve adequate quality control using prior art metalizing methods.
Silver has been used in the field of medicine to promote wound healing. U.S. Pat. No. 5,814,094 issued Sep. 29, 1998 to Becker et al., describes a system involving direct application of silver to a wound to promote wound healing. U.S. Pat. No. 4,960,413, issued Oct. 2, 1990 to Sagar et al., describes a wound dressing assembly which includes silver as an anti-bacterial agent. U.S. Pat. No. 4,728,323, issued Mar. 1, 1988 to Matson, describes an antimicrobial wound dressing comprising a substrate, such as a bandage, coated with an antimicrobially effective film of a silver salt. Deposition of silver onto nylon or other medical grade fabric using conventional autocatalytic methods may result in areas of the fabric having greater or less than the intended amount of silver coated thereon. An uneven silver coating is undesirable for medicinal quality silver coated bandages. There is a need for a process that results in a relatively thin and uniform application of metal ions, such as silver, to a substrate such as wound dressing materials.
In order to guarantee a minimum deposition of silver onto material, such as wound care dressings, according to conventional autocatalytic methods, it is necessary to increase the concentration of silver in solution. This ultimately increases the overall cost of processing the material. Further, an increase in the concentration of silver in solution can result in clumping and scaling of silver, and may cause voids or gaps in silver deposition. To guarantee a minimum coverage of silver onto material it is necessary to increase the time the material is exposed to a conventional autocatalytic solution. This results in a reduction in the amount of material processed per hour, which affects processing price accordingly.
The aerospace industry uses metals and metalized fabrics for impedance, resistance, RF resonance, RFI—EMI shielding, conductivity levels, low observability applications, thermal signature reduction and transfer, and infrared signature reduction requirements. Parasitic metals, such as copper foil, are presently in use in aerospace applications. Parasitic metals significantly increase the weight of an aircraft. Metalized materials produced by conventional autocatalytic processes do not produce the conductivity levels desired by the industry. Work hardening may also be a problem when applying metal to a flexible component using prior art methodology.
It is, therefore, desirable to provide a process for deposition of metals onto a material that results in a uniform and controlled application of metal onto the material.